Mastering Data Analytics Interview: Top Questions and Answers for Fractal Analytics

February 16, 2024

Aspiring to join Fractal Analytics, one of the leading firms in data analytics, is an exciting endeavor for many professionals. However, preparing for the interview can be daunting. To help you navigate this process successfully, we’ve compiled a comprehensive guide featuring essential data analytics interview questions and insightful answers tailored for Fractal Analytics.

Table of Contents

Basic JavaScript questions

Question: What is JavaScript?

Answer: JavaScript is a high-level, interpreted programming language primarily used for client-side web development. It allows for dynamic and interactive website functionality.

Question: What are the data types in JavaScript?

Answer: JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol (added in ECMAScript 6). Additionally, there is the object data type, which includes arrays, functions, and objects.

Question: What is the difference between null and undefined?

Answer: null represents the intentional absence of any value, while undefined represents the absence of a defined value. null is typically assigned by developers to signify no value, whereas undefined is the default value for uninitialized variables.

Question: What are closures in JavaScript?

Answer: Closures are functions that have access to variables from their outer lexical scope even after the outer function has finished executing. They are created whenever a function is defined within another function and has access to the outer function’s variables.

Question: What is this keyword in JavaScript?

Answer: This keyword refers to the execution context of a function and depends on how a function is called. In the global scope, this refers to the global object (e.g., window in a browser). Inside a function, this refers to the object that is called the function.

Question: What is event delegation in JavaScript?

Answer: Event delegation is a technique in JavaScript where you attach a single event listener to a parent element rather than attaching multiple event listeners to individual child elements. This is useful for improving performance and handling events for dynamically created elements.

Question: Explain the difference between == and === in JavaScript.

Answer: == is the equality operator and performs type coercion, meaning it converts the operands to the same type before comparison. === is the strict equality operator and does not perform type coercion, so it checks both value and type equality without conversion.

Python-related Questions

Question: What is Python?

Answer: Python is a high-level, interpreted programming language known for its simplicity and readability. It supports multiple programming paradigms, including procedural, object-oriented, and functional programming.

Question: What are the data types in Python?

Answer: Python has several built-in data types, including int (integer), float (floating-point number), str (string), bool (boolean), list, tuple, dict (dictionary), and set. Additionally, Python supports complex numbers (complex) and the None type.

Question: Explain the difference between list and tuple in Python.

Answer: Lists (list) are mutable, ordered collections of elements, while tuples (tuple) are immutable, ordered collections. This means that you can modify the elements of a list after it’s created, but you cannot modify the elements of a tuple.

Question: What is a dictionary in Python?

Answer: A dictionary (dict) in Python is an unordered collection of key-value pairs, where each key is unique and associated with a value. It is used for mapping keys to values and is commonly used for fast lookup and storage of data.

Question: What is a lambda function in Python?

Answer: A lambda function is an anonymous function defined using the lambda keyword instead of the def keyword used for regular functions. It can take any number of arguments but can only have one expression. lambda functions are often used as arguments to higher-order functions like map(), filter(), and sorted().

Question: Explain the difference between == and is in Python.

Answer: The == operator compares the values of two objects, returning True if the values are equal, while the is operator checks whether two variables refer to the same object in memory, returning True if they do.

Question: What is a generator in Python?

Answer: A generator is a special type of iterator in Python that allows you to generate a sequence of values lazily, one at a time, rather than storing them all in memory at once. They are created using the yield keyword within a function, and they provide memory-efficient iteration over large data sets.

Question: Explain the concept of list comprehension in Python.

Answer: List comprehension is a concise way to create lists in Python using a single line of code. It allows you to iterate over an iterable (such as a list or range) and apply an expression to each element to generate a new list. List comprehensions can also include conditions for filtering elements.

Question: What is the difference between append() and extend() methods in Python lists?

Answer: The append() method is used to add a single element to the end of a list, while the extend() method is used to add multiple elements (from an iterable like another list) to the end of a list, effectively extending the list.

SQL-related Questions

Question: What is SQL?

Answer: SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases. It allows users to perform tasks such as querying data, updating data, inserting new data, and deleting data from a database.

Question: What are the different types of SQL commands?

Answer: SQL commands can be broadly categorized into four types:

Data Definition Language (DDL): Used to define, modify, and delete database objects such as tables, indexes, and views. Examples include CREATE, ALTER, and DROP.

Data Manipulation Language (DML): Used to retrieve, insert, update, and delete data from tables. Examples include SELECT, INSERT, UPDATE, and DELETE.

Data Control Language (DCL): Used to control access to data within the database. Examples include GRANT and REVOKE.

Transaction Control Language (TCL): Used to manage transactions within the database. Examples include COMMIT, ROLLBACK, and SAVEPOINT.

Question: What is a primary key in SQL?

Answer: A primary key is a unique identifier for a record in a table. It ensures that each record in the table is uniquely identifiable and that there are no duplicate entries. A primary key column cannot contain NULL values, and each table can have only one primary key.

Question: What is a foreign key in SQL?

Answer: A foreign key is a column or a set of columns in a table that establishes a link between two tables. It creates a relationship between the tables by referencing the primary key or a unique key of another table. This ensures referential integrity, meaning that values in the foreign key column must match values in the referenced primary key column.

Question: What is the difference between INNER JOIN and LEFT JOIN in SQL?

Answer: INNER JOIN returns only the rows that have matching values in both tables based on the specified join condition. It excludes rows from both tables that do not meet the join condition.

LEFT JOIN returns all the rows from the left table (the first table specified in the query) and the matching rows from the right table based on the join condition. If there are no matching rows in the right table, it returns NULL values for the columns from the right table.

Question: What is a subquery in SQL?

Answer: A subquery, also known as a nested query or inner query, is a query nested within another SQL query. It can be used to retrieve data from one or more tables based on specific conditions. Subqueries can be used in SELECT, INSERT, UPDATE, and DELETE statements and can return single or multiple values.

Question: What is normalization in SQL?

Answer: Normalization is the process of organizing data in a database efficiently by reducing redundancy and dependency. It involves dividing large tables into smaller tables and defining relationships between them. Normalization aims to minimize data duplication and ensure data integrity, making it easier to maintain and update the database.

Questions based on ML

Question: What is machine learning?

Answer: Machine learning is a subset of artificial intelligence (AI) that focuses on the development of algorithms and models that allow computers to learn from and make predictions or decisions based on data. It involves training models on historical data to identify patterns and relationships, which can then be used to make predictions or decisions on new data.

Question: What is overfitting in machine learning? How can it be prevented?

Answer: Overfitting occurs when a machine learning model learns to capture noise or random fluctuations in the training data rather than the underlying patterns or relationships. This leads to poor generalization performance on new, unseen data. Overfitting can be prevented by:

Using more training data to capture a broader range of patterns.

Simplifying the model by reducing its complexity or adding regularization techniques such as L1 or L2 regularization.

Applying techniques such as cross-validation or early stopping to monitor and prevent overfitting during model training.

Question: What is a Random Forest?

Answer: Random Forest is an ensemble learning algorithm used for classification and regression tasks. It constructs multiple decision trees by randomly sampling both data points and features. By averaging predictions from these trees, it reduces overfitting and improves accuracy. This approach is robust to outliers, noise, and irrelevant features, making it widely applicable in diverse fields like finance and healthcare.

Question: What is a Decision tree?

Answer: A decision tree is a popular machine-learning algorithm used for both classification and regression tasks. It’s a flowchart-like structure where each internal node represents a feature or attribute, each branch represents a decision rule, and each leaf node represents the outcome or label. Decision trees recursively split the dataset into subsets based on the most informative features, aiming to create homogeneous subsets that result in the purest possible classes or the least variance in regression. They’re easy to interpret and visualize, making them useful for understanding decision-making processes in various domains.

Question: What is Data structure and analytics?

Answer: Data structures refer to the way data is organized and stored in a computer, such as arrays, linked lists, trees, and graphs. Algorithms, on the other hand, are step-by-step procedures or methods for solving computational problems or performing tasks efficiently, including searching, sorting, and graph traversal. Together, data structures and algorithms form the core foundation of computer science and programming, essential for designing efficient and scalable software solutions.